fix lint

Author: yokomotod

gokart/gcs_config.py

@@ -1,7 +1,7 @@
 try:
-    import google.auth
-    import httplib2
+    import googleapiclient  # noqa: F401
 except ImportError:
+    # sentinal: this file should not be imported if [gcs] extra is not installed.
     raise
 
 import json

gokart/s3_config.py

@@ -1,7 +1,7 @@
 try:
-    import botocore
-    from boto3.s3.transfer import TransferConfig
+    import boto3  # noqa: F401
 except ImportError:
+    # sentinal: this file should not be imported if [s3] extra is not installed.
     raise
 
 import os

test/test_target.py

@@ -17,7 +17,7 @@
 
 try:
     import boto3
-except:
+except ImportError:
     pass